(a) Field of the Invention
The present invention relates in general to image projection systems. More particularly it relates to a head mounted image projection system that is compact, simple and easily implemented.
(b) Description of Related Art
A variety of image projection systems are known in the art. In general, such systems use a variety of lens and other optics to project a relatively small conventional screen image onto a substantially larger screen. One of the best known examples of this type of system is projection television.
Head mounted image projection systems are particularly advantageous. They are often used in virtual reality systems for entertainment and non-entertainment applications (e.g., training and simulation). A typical flight simulation system includes a computer that executes software programs that create the flight simulation images. These images are coupled via a video cable to floor-mounted light value projectors, which in turn feed the image to fiber optic image guides. The fiber optic image guides couple the image to an optics configuration mounted on a helmet or other headgear. The user places the headgear on his/her head, and the optics configuration projects the image onto a screen located in front of the user. Alternatively, the user may view a magnified virtual image by using a simple magnifier or an eyepiece, as used in microscopes and telescopes (one such system is available under the trademark "Fiber-Optic Helmet Mounted Display" and is marketed by CAE Electronics Ltd. Of Saint-Laurent Quebec, Canada). Other projection systems are disclosed in U.S. Pat. Nos. 4,347,508; 4,922,550; 5,416,876; 4,439,157; and 5,319,490.
The above-described systems have several shortcomings. For example, the floor mounted projector is large, consumes several kW of power, relatively immobile and expensive. The fiber optic image guide, when provided in sufficient length to provide the user with some mobility, can be cumbersome, lossy in terms of luminance and resolution, expensive and relatively heavy. The optics configuration can become extremely complicated, large and expensive depending on the size of the projected image and the desired image resolution which is defined as the smallest discernible or measurable detail in the image. The excessive weight on the head can be a significant deviation from the operational environment being simulated.
Accordingly, there is a need for a head mounted image projection system that is compact, lightweight, inexpensive and relatively easy to design and maintain.